FWIW I have wanted to do this many times and it seems natural. I had guessed that the reason it wasn't implemented was that it requires the under operation to maintain state in some sense (the shape of the original input before flattening).... out of curiosity, are there any other verbs that do this?
Jonah On Sat, Oct 14, 2023 at 5:23 AM Henry Rich <henryhr...@gmail.com> wrote: > This seems like a useful feature and not difficult to implement. We can > discuss here what should be supported. > > Morten's reservations (in the cited article) are reasonable. I note that J > has semiduals, and that it would make sense to support structural under for > dyads using semiduals. > > Henry Rich > > On Sat, Oct 14, 2023, 6:10 AM LdBeth <andp...@foxmail.com> wrote: > > > >>>>> In <ngekbkd--...@tutamail.com> > > >>>>> "'Viktor Grigorov' via Programming" <programm...@jsoftware.com> > > wrote: > > > > > Why does > > > > > (|. &. ,) i.3 3 > > > > > result in a domain error (likewise with &.:), while > > > > > ($ $ (|. @ ,) ) i.3 3 > > > > > doesn't? > > > > The domain error is raised by ,^:_1 and as in J and APL > > the inverse of ravel is not defined in present time. > > > > This is not the first time people asking about this feature > > and the APL community have given this a name "structural under" > > > > https://www.dyalog.com/blog/2023/01/structural-vs-mathematical-under/ > > > > >> ... an important reason was that Roger Hui wasn’t a big fan of the > > >> proposed extension known as “structural under” > > > > ldbeth > > > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
